LiVOPO4 is known as a compound that can realize a 4-V-class charge-discharge voltage among phosphate-based positive electrode materials. However, lithium ion secondary batteries that use LiVOPO4 have not achieved sufficient reversible capacities or rate characteristics. This positive electrode material is, for example, disclosed in PTL 1, PTL 2, and NPL 1 to NPL 4 below. Crystals represented by structural formula LiVOPO4 are known to undergo reversible lithium ion intercalation and de-intercalation. According to PTL 1, the discharge capacity of a nonaqueous electrolyte secondary battery is larger when β-type crystals of LiVOPO4 are employed than when α-type crystals (triclinic crystals) of LiVOPO4 are employed.